Manufacture of oxidation products of hydrocarbons



Jari. 1, 1929.

F. J. CARMAN MANUFACTURE 0F OXIDATION PRoDUc'rfs 0F HYDRocARBoNs FiledAug. e, 1925 *0369i 0500@ USM 5% 95:50,@

Fra/wals J O'wrman PSW "a atl'ozuwql Patented Jan. l, 1929.

,UNITED STATES FRANCIS J'. CARMAN, OF NEW YORK, N. Y.

MANUFACTUBE OF OXIDATION PRODTJ'C'IS OE HYDROCABBONS.

Application iled August 6,1923. Serial No. 656,085.

This invention relates Ito manufacture of l,oxidation products ofhydrocarbons; and it relates more articularly to processes in whichhydrocarl; the halogen `derivatives oxidized, most advantageously withthe aid of suitable catalysts, but not necessarily so, under conditionsfavoring production of fthe desired oxidation products from thehydrocarbons. More specifically, the invention relates .to

the manufacture of aldehydes, and particularly formaldehyde, byprocesses of this general character.

The principles of the invention are be- A lieved applicable to limitedoxidation of hydrocarbons generall and in its broader aspects theinvention 1s therefore to be viewed as not restricted to the treatmentof any specific class or series of hydrocarbons. Its

greatest present utility is in themanufacture of aldehydes fromaliphatic hydrocarbons, particularly the paraiiin series ofhydrocarbons, and specifically in the manufacture of formaldehyde frommethane. Accordingly the manufacture of formaldehyde from methane willbe more particularly hereinafter referred to and described as anillustrative example by means o'f which a full understanding of theprinciples underlying the invention ma be afforded'.

It is to be understoo however, that other hydrocarbons, not necessarilyaliphatic but characterized by the presence ofone or more paraffinradicals or groups in the molecule, are susceptible of treatment inaccordance with the invention to produce useful prodplet of limitedoxidation, especially aldey es.

Attempts have been made heretofore to produce intermediate oxidationproducts of the paraffin or saturated hydrocarbons by reacting directlythereupon with oxygen, but the diiiiculty is that oxygen does not reactwith them except at, temperatures where it also reacts too vigorouslywith the desired final products for any appreciable yields of the latterto be recovered. Thus it is that, in the manufacture of formaldehyde,for ex-` ample, present commercial methods are of 5o quite a differenttype not involving the use Y of methane itself. Y

'It is a principal object of the present invention to enableintermediate oxidation products of hydrocarbons to be obtained byoxidizing'said hydrocarbons under such conditions as to render theoxidation suscepti-4 ons are halogenated' andble of regulation andcontrol, whereby the desired oxidation products are recoverable insubstantial quantities, thus making possible the commercial productionof intermediate oxidation products. of the character described, usingthc parent hydrocarbons themselves as starting material, and thusavoiding the use of more costly derivatives which must be 'relied uponas starting material in processes heretofore known. A further and morespecific object of the invention is to enable for'maldehyde tobe-manufactured directly from methane or lgaseousI mixtures, such asnatural gas, containing` methane. A

With the foregoing objects 1n view, as

well as others which will become apparent as the disclosure proceeds,the invention comprises the novel process and process steps hereinafterdisclosed and explained in connection with a specific' illustrativeexample to which, however, it is to be understood the invention in itsbroader aspects is not restricted. l

Y Generally described, the process of the invention comprises acarefully controlled and regulated oxidation of hydrocarbons, inthecourse of which oxidation the hydrocarbons pass through, or may beconsidered-tol pass through, a transition stage in which they exist inhalogenated form as the result of what may be termed' an initialoxidation. Further oxidation results in splitting off the correspondinghydrogen halid and producing the ldesired intermediate oxidation productof the particular hydrocarbon in question; while oxidation of thehydrogen halid regenerates the halogen which can be used,

to halogenate more of the hydrocarbon and thus maintain a cyclicalprocess. In the case of manufacturing formaldehydefrom methane, andassummg that the halogenating agent employed is chlorine, berepresented, for purposes ofexplanation, by .the following reactions:

Within the scopeA of the invention as viewed in its broader aspects,these reactions maybe carried out: separately and in the orderindicated, But it is'of great advantage in practice to carry out allthree reactions simultaneously or substantially so, especially when thisis clone 'th the aid of the process may a catal st as will be more fullyhereinafter pointe out. Itis to be understood that 1n speaking ofcarrying out these reactions simultaneously, it is not intended toassert that the chemical action as it actually occurs necessarilyfollows the precise reactions here given, these merely representing in aconvenient manner one way of explaining what takes place. The exactmechanism of the chemical reactions occurring when the process iscarried out in practically one stage, instead of in the three stagesrepresented by the above explanatory reactions, may be more or lesscomplex and cannot readily be determined with certainty. Furthermore thereactions by which the intermediate oxidation product is obtained are inpractice accompanied to` a greater or less extent by side-reactions suchas further chlorination to polychlor-derivatives, and oxidation of theseand of formaldehyde and other oxygen derivatives to carbon monoxid,carbon dioxid and Water.

By proceeding in accordance with the invention as ,v generally set forthabove, the

desired `oxidationof the hydrocarbon starting material may be effectedat relatively low temperatures and is susceptible of reasonably accuratecontrol and regulation; with the result that it is possible to produceand recover substantial yields of the desired intermediate oxidationproducts from the reaction gases. o

The initial oxidation of the hydrocarbon by halogenation can be effectedquickly and i quantitatively at comparatively low temperatures, theextent of the halogenation depending upon the relative concentrations ofthe gases, the action of light, and the presence or absence ofcatalysts, as well as Aon the temperature. The symmetry of theVhydrocarbon molecule having once been broken, the resulting compoundsare then much more readily susceptible to the action of oxygen.Accordingly, by initiating the ,A

oxidation ofthe hydrocarbon through chlovrination,`for example, and thentreating the resulting chlorine derivative with oxygen to produce thedesired oxygen derivative, such oxygen derivative can be obtained fromthe hydrocarbon Without at any time exceeding relatively low .operatingtemperatures, thus permitting recovery of good yields of said oxygenderivative. The hydrogen chlorid split olf in oxidizing the chlorinederivative may'be wholly o'r largely oxidized to regenerate chlorine forre-use in chlorinating more of the hydrocarbon. By causing these.severa1 operations to occur simultaneously,y a certam proportion ofchlorine will therefore su'ice for the resultant oxidation of more Aofthe hydrocarbon than corres nds tothe proportion of the primary-chorine. derivative consumed. l

' A concrete example illustrating'how the process of the invention maybe applied to the manufacture of formaldehyde `from methane will now begiven, reference being also made to the accompanying drawing whichrepresents more o r less diagrammatically a system of apparatus suitablefor use in carrying out the process. Gases resulting from a previousoperation, contained in gasometer 1l, are mixed with fresh gases inmixing chamber' l, namely, methane, chlorine and oxygen, said freshgases being introduced through the correspondingly designatedvalve-controlled pipes as shown 0n the drawing. In the mixing chamber l,the gaseous (i. e. gaseous or vaporous) mixture is preheated to arequisite temperature gases are then scrubbed with 4water in anabsorption tower 5, filled with coke or other suitable material. Thewater from tower `5 collecting in receiver 6, together with thecondensate collecting in receiver 4, is worked up for its formaldehydeand hydrochloric acid content. vThe gases leaving the top of tower 5 areconducted into another tower 7 where they are dried by means ofconcentrated sulphuric acid or other suitable drying agent. The driedgases then pass into a reaction chamber 8 containing a catalyst foroxidizing any earbon monoxid to dioxid, suitable catalysts for thispurpose being cobalt sesquioxid or mixtures of copper and manganeseoxids. fter passing through reaction chamber 8, the gases are nextconducted to and through another absorption tower 9 Where they areexposed to milk of lime, or sodium or potassium carbonate, to remove thecarbon dioxid content. A suction blower 10 pulls the residu al gasesfrom this tower 9 and directs them to gasometer 11 from which they areled back as needed to mixing chamber 1., thus completing the circuit.

It is to be understood that the application of legends to the'drawingsis not/intended to be in any sense restrictive, but is made only for thepurpose of renderingl still clearer the specific embodiment of theinvention chosen to illustrate the broad principles involved.

The oxygen employed may-be either. the pure gas or air, or mixtures ofthese in any suitable proportions; but it is advantageous to use pureoxygen because, among other things,this obviates the necessity forhanfio dling large volumes lof inert gases. It is also to bey understoodthat the methane or other hydrocarbon employed may be either the puregas or may be accompanied by other hydrocarbons. Natural gas may be usedto furnish methane for the process. Instead of introducing free chlorineinto the mixing chamber, hydrogen chlorid may be introduced, it beingonly necessary to provide chlorine in available orV reactive form, underthe conditions of operation.

While it has been greater percentage conversion of methane toformaldehyde is possible in the present process than has been obtainedheretofore by the action of oxygen alone, yet even in the presentprocess there is a practical limit beyond which the proportion of gasentering into reaction may .not be profitably ushed, for in higherconcentrations a point of equilibrium is reached Where the formaldehydexdecomposes as fast as it is formed. For this reason itis of greatadvantage practically to carry out the reactions cyclically asdescribed, and to subject to the action of the catalyst a second timethe gases thatv previously passed through unchanged, removing theproducts of oxidation by absorption in suitable media and making up thelosses by additions of .fresh gases.

A variety of different catalysts 'are available for use in carrying outthe process of the invention, where a catalyst is necessary ordesirable,as is usually the case. In general, metallicv oxids or halids aresuitable; but some that are good catalysts for the conversion of methylchlorid into formaldehyde are less effective in the'oxidation ofhydrogen chlorid or are apt to cause too energetic oxidation offormaldehyde. More stable or fixed chlorids 4are distinctly bettercatalysts in the present process, especially the fixed halids ofdivalent metals of the alkaline earth group. The chlorids of calcium,barium and strontium are particularly effective catalysts for the`purposes present invention, and of these, barium chlorid is ordinarilymost satisfactory. The alkaline earth metal chlorids are most effectiveas catalysts in the present process when the temperature and reactionchamber is maintained at from 400. to 500 C; vAt

such temperatures they are very effective in aiding conversion of methylchlorid into formaldehyde in the presence o f oxygen and methane, andat-the same time they assist in the oxidation of most of the hydrogenchlorid to chlorine which is at once absorbed by the Lmethane present toform methyl chlorid. As between the oxids and the chlorids, the chloridsafford some advantage in that they have less tendency than the oxids tocause destructivedecomposition of the desired hydrocarbon oxidationproduct sought. Generally speaking,

found Jthat a much- 4be the oxid.

4tice. of the invention,

of the non-volathe invention is to be understood as signify-- ing thatcompound of a divalent element For the purposes of the present used as acatalyst Which' results from conv tinued action of the reacting gases atthe reacting temperature upon the oxid of said element. In the case ofbarium, calcium or strontium, pound Will be the chlorid under theparticular reacting conditions hereinafter set forth; While withberyllium or magnesium it will Any Well known or suitable Way may beresorted to for bringing a large surface of the-catalyst into contactWith the gas mixtures, such as deposition upon asbestos, pumice or otherporous material,

Whether 1t is a catalyst Vor not;y for in this process, as Well asothers employing catalysts, the effective catalytic activity of. anyofthe materials used depends in large measure upon the ext-ent of thesurface exposed to the gases.

As already pointed outa it is not advisable from an economic standpointto attempt to push the percentage conversion of the methyl chlorid 'intoformaldehyde too farf in a single passage of the gaseous mixture incontact with the catalyst. In the practherefore, it -is best to operateat what may be determined to be the most economical conversion rate andto re-pass the mixture repeatedly in contact with the lcatalyst in thereaction chamber cyclically, the gases traveling in a circuit. In thusoperating, the lresultant formaldehyde is removed fromthe reaction gasesWater; residual after each pass, aswell as at a later point hydrogenchlorid, etc.; and

in the c1rcu1t fresh methane, chlorine and'4 oxygen are introduced insuch quantities as maybe necessary to restore substantially the originalproportions of the gases in the mixture passed over the `catalyst, 'andto for example, such resultant commaintain the production' lofformaldehyde',l

reasonably constant. ver met aneunder the conditions herein set forthto4 form methyl chlorid, the gaseous mixture supplied to the reactionchamber 2 can be considered for all practical purposes to consist ofmethyl chlorid, methane and oxygen As chlorine ycombines .y readily andquantitatively with the in predetern'xined proportions. There should bea large excess of methane in order that I the chlorine regenerated byoxidation of the hydrogen chlorid split off from the methyl 5 chloridmay immediately re-combine with more methane to form methylfchloridnAccordingly, in a ractical embodiment of the novel process w ich hasgiven good results, the proportions ofthe gases in the mixture suppliedto the catalytic reaction chamber are so adjustedy by regulating the.feed of fresh gases that the mixture consists of four parts of methane,one part'. of oxygen, and one part of methyl chlorid or its equivalentin methane and available chlorine, all parts being by volume.A Passingthis mixture over powdered barium chlorid at about 480o C., and allowingthe mixture to contact with the e. catalyst for a sufficient time, sayfor 5 seconds or thereabouts by Way of example, converts in-one passagebetween 8 and 10 per cent of the methyl chlorid to formaldehyde, Whlleat the same time to a somewhat larger proportion of the methyl chloridis oxidized to carbon monoxid and carbon dioxid. Concomitantly thehydrogen chlorid liberated by oxidation of the methyl chlorid isoxidized to chlorine which, combining with the excess of methanepresent, regenerates e :50 methyl chlorid. .In 'normal practical Worklngof the process under the conditions as-l sumed in this specificexample', all of the hydrogen chlorid is oxidized with the exception ofan amount equal to about 0.85

per cent of the methyl chlorid'content of the gaseous mixture su pliedto the reac- -vtion chamber; so that tiie loss `of available chlorine ineach pass is comparatively slight even if the hydrochloric acidcollected with 40 the formaldehyde removedfrom the effluent gases beallowed to waste. After the described catalytic oxidation of carbonmonoxid to carbon dioxid, if this be necessary, and the removal of thecarbon dioxid, the gaseous mixture sent by the blower 10 back to thereaction chamber by way of the gasometer 11 therefore still consists lofmethane, oxygen and methyl'chlorid but in proportions differing fromthose of Y l5o the original mixture due to the oxidizing `L.reaction andthe small loss of chlorine as hydrochloric acid. By `properly adjustingthe feed of fresh methane, oxygen andchlorine into' thesystem, inadvance ofthe 5 5 mixing and reaction chambers, the original proportionsof the gases may be approxi-v mately restored and, the other conditionsof operation being maintained uniform, the output of formaldehyde can bekept 'substantially constant at therate found to be fthe best forprofitable operation of the 4process.

The isolation of the formaldehyde which is condensed and absorbed,together with 05 water'and hydrochloric acid, from the cir- `tate may bedehydrated with concentrated temperature, addin salt as may beneces saryto lower the freezing point of the fluid to a point at which theolymerization and precipitation is rapid. f it is found desirable torecover the hydrochloric acid present in the aforesaid condensate, l thefiltrate from the polymerized formaldehyde precipisulfuricacid and thehydrogen chlorid reintroduced into the circulating gases. Under ordinarycommercial conditions, however, the relatively small proportion (e. g.10%) of hydrogen chlorid escaping re-conversion to methyl chlorid in the.normal operation of the process in its morev efficient forms can beotherwise more economically replaced.

Other halids such as the iodid or bromid maybe used instead of, orinconjunction with, methyl chlorid; but experience thus far has shown thechlorid to be far the most advantageous and its use is therefore to berecommended in practice.` e

In the treatment of more complex hydrocarbons than methane, theproduction and recovery of any single intermediate oxida- -tionv productis sometimes rendered more diliicult vby reason of the possibility ofhalogen substitution indifferentA positions in the molecule, thusrendering the production of mixtures of oxidation products likely. Thisis of course unobjectionable where the production of a sin le oxidationproduct 1s not essential. In t e case of homologues closeto methane, theliability to production of mixtures ofv oxidation products is not sopronounced and it is feasible, for example,

to prepare acetaldehyde from ethane by the presentv process. What Iclaim is:

1. Inthemanufacture of partial oxidation products of hydrocarbons, the'process which comprises heatinga gaseous mixture of a hydrocarbon,available oxygen and an available halogen in a suitable reaction chamberto temperatures favoring limlted oxidation# of the hydrocarbon, andseparating a desired -oxidation product of said hydrocarbon from the'reaction gases leaving. said chamber, 'at least` a substantial. portionof said halogen being made availablein the t oxidation and again usedfor. reaction with further quantities of said hydrocarbon.

- 2. rlhe process set forth in claim 1, further characterized by theemployment inthe reaction chamber of a catalyst favoring oxida tionunder the'condition's prevailing'in said chamber. t y

3. In the manufacture of aldehydes, the d process' which compriseshalogenating a hydrocarbon to obtain4 a mono-halogen derivative thereof,and oxidizingA the resultant mono-halogen derivative to obtain thedesired aldehyde.

4. In the manufacture of aliphatic aldehydes, the process whichcomprises halogenating an aliphatic hydrocarbon to obtain a mono-halogenderivative thereof, and oxidizing the resultant mono-halogen deriva tiveto obtain the desired aldehy-de.

5. In the manufacture of formaldehyde,

the process Which comprises halogenating methane to obtain methyl halideand oxidizing resultant methyl .halide to formaldehyde.

6. In the manufacture of formaldehyde, the process which compriseschlorinating methane to methyl chlorid and oxidizing such methyl chloridto formaldehyde.

7. In the lmanufacture. of formaldehyde, the process which compriseshalogenating methane to obtain methyl halide and oxidizing resultantmethyl halid to formaldehyde in the presence of a'catalyst favoringconcomitant oxidation of resultant hydrogen halid and liberation ofthehalogen.

8. In the manufacture nof formaldehyde, the process'` which compriseshalogenating methane, oxidizing resultant methyl halid to formaldehyde,and oxidizing resultant hyldrogen halid torender the halogenavailab e,stantiallysimultaneously in the presence of a catalyst comprising areaction-promoting compound of a divalent element, removingformaldehyde, and utilizing the resultant available halogento halogenatemore methane.

9. In the manufacture of formaldehyde,-

the process which. comprises heating to a. reacting temperature agaseous mixture com'- prising methyl halid, methane r`and oxygen,

and recovering formaldehyde from theresultant reaction gases.

10. In the manufacture of formaldehyde, the process which comprisesheating to a gaseous mixture camprising methyl chlorid methane andoxygen, and recovering formal sultant reaction gases.

11. In the manufacture. of formaldehyde, the process which comprisesheating to a reacting temperature a gaseous mixture comprising methane,methylhalid and oxygen, in the presence of a catalyzer for the oxida.tion of hydrogen halid, separating re. sultant formaldehyde, adding moremethane and oxygen to the residual mixtureof gases, and repeatin fthefheating operation and the separation o formaldehyde, cyclically.

12'. In the manufacture of rformal ehyde, the process which comprisesheating to a reacting temperature a gaseous mixture comtion products ofhydrocarbons, the process prising methane, methyl chlorid and oxygen allthese" reactions being effected sub,

dehyde from the re-v i which comprises in the presence of a catalyticcom ound of an alkaline earth metal, said met ane being present inlarger volume than either of the other gases, separating resultantformaldehyde from the reaction gases, and re-treating the residual gasesfor production of more formaldeh de.

13. In t e manufacture of formaldehyde, the process which comprisesheating -a gaseous mixture comprising methyl chlorid and oxygen to anoxidizing temperature at which formaldehyde can exist, and recoveringresultant formaldehyde.

14. In -the manufacture of formaldehyde,

the process which comprises reacting upon methyl chlorid With oxygen ata temperature Within the approximate range of 400 C. to

p100; C., and recovering resultant formaldey15. In the manufacture offormaldehyde, the process which comprises passing a mixture containingpredetermined proportions of methane, methyl chlorid and oxygen over a`metal at a temperature within the approximate range of 400D C. to 500C., separating formaldehyde from the effluent gases, adding methane,oxygen and available chlorinev to the residual gases as may be necessaryto restore approximately the original p-roportions of methane, met ylchlorid and oxygen,

and repeating the foregoing operations for production of moreformaldehyde in a continuous cyclical procedure.

16. In the manufacture of formaldehyde, the process set forth in claim15, 'further characterized by the fact that the catalytic compoundemployed is a reaction-promoting compound of an alkaline earth metal.

17. VIn thegmanufact-ure of formaldehyde, the process set forth -inclaim 15, further characterized by? the fact that the catalytic compoundemployed is barium chlorid.

18. In the manufacture of' formaldehyde, the process set forth in claim15, further characterized by the fact that the catalyticcompound'employed is barium chlorid and that the reaction temperature ismaintained at about 480? C. l

19. In the manufacture of'formaldehyde, the process' set forth in claim15, further characterized by the fact that the mixture passed over said'catalytic compound comprises about four parts methane, methyly chloridand one part oxygen, by volume. l y I 20. In the manufacture of partialoxidation products of hydrocarbons, the process halogenating ahydrocarbon inheated gaseous condition and cxidizin the resultanthalogen derivative to split o hydrogen halid and form the desiredoxidation product.

21. In the manufactme of partial oxidaone part which compriseshalogenating a hydrocarbon in heated gaseous condition in the presenceof available oxygen and of a catalyst aiding' oxidation of hydrogenhalid, an.v excess of said'hydrocarbon being also present, andseparating a desired oxidation product from the reaction gases,

22. In the manufacture of partial oxidation products of paraiiinhydrocarbons, the process which comprises halogenating and oxidizing aparaffin hydrocarbon in gaseous conditionwith the aid of a catalystcomprising a *reaction-promoting compound of a divalent element.

23. In the manufacture of partial oxidation produc-ts of paraffinhydrocarbons, the process which comprises chlorinating and oxidizing aparaiindiydrocarbon with the aid of a catalyst comprising bariumchlorid.

24. In the manufacture of formaldehyde, the process which compriseshalogenating and oxidizing methane with the aid of a catalyst comprisinga reaction-promotingA compound of a divalent element.

N25. In the manufacture of formaldehyde,

the process which comprises chlorinating and oxidizing methane with theaid of a catalyst comprising barium chlorid.

26. In the manufacture of formaldehyde, the process which comprisesheating a gas. eous mixture comprising methyl chlorid and oxygen to anoxidizin temperature at which formaldehyde can exlst, in the presence ofa catalyst comprising a reaction-promoting compound of a divalentelement, and recovering resultant formaldehyde.

27. In the manufacture of formaldehyde, the process which .comprisesreacting upon methyl chlorid with oxygen at a temperature withintheapproximate range of 400 C. to 500 C. in the presence of a catalystcomprising a reaction-promoting compound of 'a divalent element, and.recovering resultant formaldehyde..

Y In testimony whereof I hereunto afxmy signature.

4FRANCIS J. CARMAN;

